CHONGQING, China -- Wandering around in downtown Chongqing, it is hard to imagine that this is a city that is going green. Vehicles clog roads in every direction. Construction cranes stretch to the horizon. But Chongqing is more than meets the eye. After living with acid rain and toxic smog for decades, the city has been scrambling for ways to clean up the air. It is also overhauling its power-hungry economy and rebuilding it on a base of industries that use less energy.